Heart disorders are a common cause of death in developed countries. They also impair the quality of life of millions of people and restrict activity by causing pain, breathlessness, fatigue, fainting spells and anxiety. The major cause of heart disease in developed countries is impaired or inadequate blood supply to the heart. The coronary arteries may become narrowed due to arteriosclerosis and part of the heart muscle is deprived of oxygen and other nutrients. The resulting ischemia or blockage can lead to angina pectoris, a pain in the chest, arms or jaw due to lack of oxygen to the heart's myocardium, infarction or tissue necrosis in myocardial tissue. Alternatively, and particularly with age, the extent of vascularization of the heart may diminish, leaving the heart undersupplied with oxygen even in the absence of significant arteriosclerosis.
Coronary-artery blockage can be relieved in a number of ways. Therapeutic-substance therapy, including nitrates, beta-blockers, and peripheral vasodilator drugs (to dilate the arteries) or thrombolytic drugs (to dissolve clots) can be very effective. If therapeutic-substance treatment fails, transluminal angioplasty is often indicated—the narrowed part of the artery, clogged with atherosclerotic plaque or other deposits, can be stretched apart by passing a balloon to the site and gently inflating it a certain degree. In the event therapeutic-substance therapy is ineffective or angioplasty is too risky (introduction of a balloon in an occluded artery can cause portions of the arteriosclerotic material to become dislodged which may cause a total blockage at a point downstream of the subject occlusion, thereby requiring emergency procedures), the procedure known as coronary artery bypass grafting (CABG) is the most common and successful major heart operation performed, with over 500,000 procedures done annually in America alone. A length of vein is removed from another part of the body. The section of vein is first sewn to the aorta and then sewn onto a coronary artery at a place such that oxygenated blood can flow directly into the heart. CABG typically is performed in an open chest surgical procedure, although recent advances suggest minimally invasive surgery (MIS) techniques may also be used.
Another method of improving myocardial blood supply is called transmyocardial revascularization (TMR), the creation of channels from the epicardial to the endocardial portions of the heart. Initially, the procedure used needles to perform “myocardial acupuncture,” and has been experimented with at least as early as the 1930s and used clinically since the 1960s, see Deckelbaum, L. I., Cardiovascular Applications of Laser Technology, Lasers in Surgery and Medicine 15:315-341 (1994). This procedure has been likened to transforming the human heart into one resembling that of a reptile. In the reptile heart, perfusion occurs via communicating channels between the left ventricle and the coronary arteries. Frazier, O. H., Myocardial Revascularization with Laser—Preliminary Findings, Circulation, 1995; 92 [suppl II:II-58-11-65]. There is evidence of these communicating channels in the developing human embryo. In the human heart, myocardial microanatomy involves the presence of myocardial sinusoids. These sinusoidal communications vary in size and structure, but represent a network of direct arterial-luminal, arterial-arterial, arterial-venous, and venous-luminal connections. The needle technique was not continued because the channels did not remain open, replaced by the use of laser energy to accomplish TMR.
Therapeutic-substance therapies with angiogenic growth factors may expedite and/or augment collateral artery development. Therapeutic-substance therapies, when combined with other treatments such as TMR or other injury causing methods may substantially increase the effectiveness of treatment over either treatment individually. To accomplish these needs, therapeutic-substance transfer devices for delivering precise amounts of these therapeutic-substances can enhance this healing process when coupled with an initial injury process. Surgeons who deal with minimally invasive surgical techniques, and interventional cardiologists who deal with percutaneous approaches, need devices for therapeutic-substance delivery procedures that also provide a localized injury with minimal effort or the need to introduce multiple tools or devices into the patient's body. Moreover, the therapeutic-substances used in modern medical technology are often quite expensive, potentially mixing and/or handling sensitive, and it is a new challenge to make these therapeutic-substances or other compounds readily available for precise, predetermined delivery during these advanced or other procedures while combined with other mechanical treatments such as TMR or other injury type treatments. Therefore, a unified device which provides the advantages of precise and localized therapeutic-substance delivery coupled with localized injury infliction in a region predetermined by the device with respect to therapeutic-substance delivery would be highly desired over existing methods of using two or more distinct tools or devices that do not provide for a precise and predetermined spatial relation between the sites for therapeutic-substance delivery and the site or sites for injury. The invention provided herein addresses these needs and provides these desired advantages in an efficient, minimally invasive, and cost effective manner.